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4 Ultimax 15's enough for 4200 cubic foot theater?

2K views 48 replies 16 participants last post by  chrisreeves 
#1 · (Edited)
So, this is my first DIY build, and the first set of subs for this room (which is open on one side with a stairwell to the rest of the house. I'm planning on doing the one-in-each-corner or one-at-the-center-of-each-wall setup that Toole advocates.

But now, I'm questioning myself and thinking maybe I should go with 18" ultimaxes instead. Amps have not been chosen yet.

Basically - is this setup of 4 sealed 15's going to be enough for reference levels of bass down to 20 hz?

I went with 15's rather than 18's thinking they would be more musical and accurate, given that they have smaller woofers.

*The subs are on the way, and can be returned - plus I've only ordered two of the four. I'm just second-guessing myself now.
 
#2 ·
More musical......no. Four 15's could be enough for you. Always hard to give suggestions to others when visiting this forum. Four 15's and later on add another 4 15's for dual opposed sealed. So many options to go with that its up to your where you want to start. Four 15's would be plenty for most. Simulation will tell you how many DB's you will hit before any room gain. Sometimes 18's are only a small upcharge and dont require much more room. If thats the case then go with 18's.

BUT there are lots of variables to your "will this be enough."
 
#3 ·
more musical...maybe. :) but not because of the size. the um15 is a little different design than the 18.


with an open room like that the toole concepts kind of get thrown out the window. might want to experiment with co-location up front.


4 um 15 sealed give about 116db at 20hz with no room gain. that is definitely a good start and sufficient for many. ported cabs could provide up to 12db or more spl around the tuning frequency with the same drivers, but at the cost of larger subs that may be more difficult to place optimally.
 
#5 ·
with an open room like that the toole concepts kind of get thrown out the window. might want to experiment with co-location up front.
Yeah I think I may close the room off next week to turn it into a nice left-right symmetrical closed rectangle
 
#4 ·
Thanks for the feedback - the "dual opposed sealed" would be a double bass array that I've read about on that monster thread, yes? I was thinking about that already - rather than building the subs into my walls as I see some have done with double bass arrays, just building racks for them to stand on to have two arrays facing each other. Has anyone here done that?
 
#7 ·
Ah - yes I thought the front/rear room aligned subs to even out room response was what you meant. The DBA seems like a great solution to smooth, clean bass - at least in rectangular rooms - as opposed to endless bass trapping. I wonder why it isn't more popular.
 
#10 ·
So, this is my first DIY build, and the first set of subs for this room (which is open on one side with a stairwell to the rest of the house. I'm planning on doing the one-in-each-corner or one-at-the-center-of-each-wall setup that Toole advocates.

But now, I'm questioning myself and thinking maybe I should go with 18" ultimaxes instead. Amps have not been chosen yet.

Basically - is this setup of 4 sealed 15's going to be enough for reference levels of bass down to 20 hz?


4 15's in a good sized room? Will that be enough?
Well that depends 4 15's will certainly fill out the bottom end but you will need to bring in some eq to compensate for roll off below 35hz. I am a fan of sealed subs but have had 2 15's adding 2 more helped A TON.
The um 15 is a pretty good driver I have been driving mine with 1000 watts each now for a long time with no problems or weird noises. Go BIG on amps if you have the budget and especially if you intend of staying sealed.
If you have not started building cabinets yet may I recommend ported.
The increase in output from 20-35 hz from the ported box is substantial and would probably be enough from wanting to upgrade further. The Johnny sub comes to mind.
 
#11 ·
Go BIG on amps if you have the budget and especially if you intend of staying sealed.
If you have not started building cabinets yet may I recommend ported.
The increase in output from 20-35 hz from the ported box is substantial and would probably be enough from wanting to upgrade further. The Johnny sub comes to mind.
Thanks for the ideas - choosing the right wattage is a challenge - I see subs with RMS watts all over the place.

Also I went with sealed because some people say they are more articulate and accurate. I dunno - had to start somewhere or I would be reading threads endlessly. I'm sure that these won't be my last subs . . .
 
#15 ·
I have UM-15's in my mains, 3000cuft room.

Here is what it sounds like at 800watts x 4 bass, with 1600w mids, 2400w tweeter. (Not all of that is used, just what's on tap.)


Thumps good. They are no LMS-18 or UXL-18 or FTW-21 though.
 
#16 ·
I agree with the assessment that 15s would be enough for most sane people.

However, I would go with 18s from the outset and have some insurance against upgrade-itis. It is not much more money and you should have some headroom which is very important, at least to me. Go for the 18s and don't look back.
 
#17 ·
What you are saying is so right, going with 18's is a great way to ensure 6 months later you are thinking what if I...........plus the cost difference between a 15 and an 18 is not that much.
An 18 is generally good for 3-5 more db's in output and that could make the difference between staying with what you made the first time or building another cabinet.
 
#18 ·
You guys are making me think. So there is no trade-off in sound quality with 18's at all? The only downside is some additional expense? I thought perhaps smaller subs would integrate into my system with the high frequencies better.

I'm just thinking - "Larger woofer = more mass = more momentum = more difficult to get it to play higher frequencies" - but I have almost zero experience with subwoofers.

If I'm totally wrong on the 18 vs 15 issue maybe I should go with the 18's from the outset like you guys are saying.
 
#40 ·
Look at the 18" LMS5400. It is considered one of the most musical subs out there. Go with 18's and it will end up saving you money in the long run. :) Years ago I started with a few 10's. Then moved to some 12's.Now have four 18's and kept two of the 12's and I am pretty happy, but my room is 1/3rd the size of yours. :)
 
#20 ·
Well multiple reasons:

1 - Parts Express sells a combo kit of enclosure and driver - but it's a sealed enclosure. The last thing I built was a model rocket when I was 12 - so I thought I should stick with someone else's proven design and construction quality.
2 - I have no subwoofer experience, but have read that sealed subs are more articulate and precise. Someone on this thread says that isn't true - but I dunno. I know that on Hsu's page, for what it's worth they say their sealed sub is their "most musical." This is only for home theater but I value precise sound.

But maybe I should do ported, maybe you're right.
 
#24 ·
I firmly believe that whole musicality of sealed subs is a giant load of crap. In the last few months I've had a psa xv15-se ported sub, a psa xs30-se dual opposed sealed sub, and my current llt that notnyt designed for me. The only difference between all 3 is my current sub kicks the **** out of the psa subs in output. They all had identical "character" of sound.
 
#28 ·
The UM cones are made of woven fiber, they weigh almost nothing and are strong.
Kids love denting dust caps, the UM's are almost bullet proof, you'd really have to kick the cone good to mess it up.

Two nu6000DSP's and 4 UM-18's would work good.
You can almost never have too much bass. (Too much, is almost enough.)
 
#30 ·
The UM cones are made of woven fiber, they weigh almost nothing and are strong.
But do they sound any different than the Stereo Integrities? Has anybody done a blind A/B test with these SI bargains vs more expensive drivers in the same room with the same enclosure, amps, SPL etc?

They won't be kicked or abused by kids in my theater. :)
 
#31 ·
They won't be seen - all-black bat cave with AT screen hiding two of the subs
 
#41 ·
Okay okay okay - I'm going with the SI 18's - 4 of 'em. Y'all are a bunch of delinquents I swear. You're the same guy who sold me a projector I didn't need Mike, now I have four subs larger than I need. This situation is completely out of hand.
 
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#45 ·
Ahh, those B-stocks get free shipping. That's what makes them a feat deal. Shipping on my pair of SI18s was $62.42. The Ultimax is easily competitive with that price, especially since you can get sales/discounts from PE with a little patience.

You need to figure out what amp or amps you're going to use, and if you want one or two drivers per channel, to select D4 or D2.
 
#49 ·
Well the damage is done - 4 18's ordered. :sigh: From 12 years of an 8" HTIB Sony $50 piece of crap to complete overkill in fell swoop. My mains are looking really puny now in comparison...

This all started when I noticed that I could get 176" 2.35:1 acoustically transparent screen on Amazon for less than $600 delivered. "Oh wow, what a deal" I thought to myself "This will be so much better than my 100" 16X9 screen - it's a no-brainer."

Well - 8 months, a lot of construction, a new projector and now a bunch of subwoofers later - that humongous screen sure wasn't a deal, that's for sure . . .
 
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